The principal objective of this grant, since its inception in 1998, has been to elucidate biological mechanisms that regulate the immune response to injury and infection. This led to the discovery of a neurophysiological mechanism by which the brain controls the peripheral immune system through the vagus nerve, the principle cholinergic nerve that connects the brain to the organs of the reticuloendothelial system. This discovery opened a new field of research, now termed "The Inflammatory Reflex" (Tracey KJ. The inflammatory reflex. Nature. 2002 Dec 19-26;420:853-9). Preclinical studies in animals models of sepsis, endotoxemia, ischemia-reperfusion, trauma, and shock have revealed that this pathway may be exploited to develop new therapies to treat patients with these and other diseases caused by cytokine overproduction. While these studies have clearly demonstrated a major role for this pathway in controlling cytokine release, there remain important unanswered questions about cellular, molecular, and neural mechanisms. In Specific Aim 1 we will test the hypothesis that the mechanism of cytokine suppression by the cholinergic anti-inflammatory pathway requires cholinergic neural input to cytokine producing cells in spleen. In Specific Aim 2 we will test the hypothesis that activation of cholinergic mechanisms in brain regulates cytokine release during endotoxemia, and in a standardized preclinical therapeutic model of CLP sepsis. These studies are essential to move the field forward. The concept of applying a classical neurophysiological study design (based on either electrically stimulating the vagus nerve or administering a selective neurotransmitter receptor agonist to activate a brain network) to specifically dissect a functional pathway for brain modulation of the immune response is singular, novel, and likely to provide significant new information about the nervous system control of the immune response. The Tracey laboratory, which has led the development of this field, is now particularly well suited to do these studies.